Data Structures
Boats to Save People
Find the minimum number of boats to carry people within a weight limit using sorting and two pointers, in O(n log n) time.
Data Structures
Arrays, Strings, Sliding Window, Two Pointers, Searching & Binary Search, Sorting, Linked List, Stack & Queue, Recursion & Backtracking, Trees, Heap / Priority Queue, Graphs, Dynamic Programming, Greedy, Bit Manipulation, Trie, Math & Number Theory, Design (LLD / OOP), SQL, System Design (HLD)
180 notes in 20 topics
Topics in Data Structures
Arrays 30
Strings 35
Sliding Window 35
Two Pointers 30
Searching & Binary Search 30
Sorting 25
Linked List 0
Stack & Queue 0
Recursion & Backtracking 0
Trees 0
Heap / Priority Queue 0
Graphs 0
Dynamic Programming 0
Greedy 0
Bit Manipulation 0
Trie 0
Math & Number Theory 0
Design (LLD / OOP) 0
SQL 0
System Design (HLD) 0
Notes
Data Structures
Valid Triangle Number
Count triplets that can form a triangle using sorting and two pointers, in O(n^2) time.
Data Structures
Minimum Number of Swaps to Make Sequences Increasing
Find the minimum swaps to make two arrays strictly increasing using a linear dynamic-programming scan over paired positions, in O(n) time.
Data Structures
Sentence Similarity Using Two Pointers
Check if two sentences become equal by inserting one contiguous run of words, using two pointers over the common prefix and suffix, in O(n) time.
Data Structures
Shortest Distance to a Character
Compute the shortest distance from each index to a target character using a two-pass left-then-right scan, in O(n) time.
Data Structures
Interleaving String Check
Check if a string is a valid interleaving of two others using dynamic programming (a naive two pointer greedy fails), in O(m*n) time.
Data Structures
DNA Complement Matching
Check whether a DNA strand is its own reverse complement using two pointers from both ends with base-pair matching (A-T, C-G), in O(n) time.
Data Structures
Is Subsequence Check (Two Pointer)
Check whether one string is a subsequence of another using two pointers in O(n) time and O(1) space.
Data Structures
Interview Concept: Same Direction vs Opposite Direction Two Pointers
Understand the two core two pointer patterns — opposite-direction (converging) and same-direction (fast/slow or read/write) — with when to use each in...
Data Structures
Interview Concept: Fast and Slow Pointer Technique Explained
Master the fast and slow pointer technique (Floyd’s algorithm): detect cycles, find the middle, and locate the nth node from the end, all in O(n) time...
Data Structures
Binary Search (Classic Iterative)
Classic iterative binary search on a sorted array in O(log n) time, with Python, Java and C++ code and an overflow-safe midpoint.
Data Structures
Binary Search (Recursive)
Recursive binary search on a sorted array in O(log n) time with O(log n) call-stack space, in Python, Java and C++.